Manufacture of artificial filaments and fibers from viscose



Patented Aug. 24, 1943 MANUFACTURE or ARTIFICIAL mmnvrs AND FIBERS FROMVISCOSE Heinrich Fink,

Rottweil-on-the-Neckar,

and

Gaston Piepp, Woli'en, Kreis Bitter-laid, Germany; vested in the AlienProperty Custodian No Drawing. Application October 11, 1940, Serial No.360,776. In Germany July 22, 1939 Claims. (Cl. 18 -54) This inventionrelates to the manufacture of artificial filaments and fibers of hightensile strength from viscose.

One of its objects is to provide a process for Obtaining such threads.

Another object is to manufacture these threads by using novel spinningbaths.

Still another object is the new threads obtainable by the new process.

These and other objects will be seen from the following specification.

Processes have recently become known which permit the production ofartificial filaments or fibers of high tensile'strength from viscosewithout employing strongly acid baths. Filaments, for example, having atenacity above two grams per denier have been manufactured by spinningin a spinning bath which contains, if necessary, besides ammoniumsulfate and sodium sulfate less than 7% sulfuric acid, whereby thefilaments are drawn at least 25% and decomposed to cellulose hydrate. Ithas also been proposed to swell the filament in an intermediate bathafter having left the spinning bath which contains less than 7% sulfuricacid, and then to take up or finish up the drawing operation. Asintermediate baths there were used either water or solutions of alkalinereacting substances to which were added neutral substances, inorganic ororganic compounds, alcohol, aldehydes, amines, even acids. During orafter the swelling operation the filament is hereby drawn 25-100%, ormore of its original length and is finally decomposed to cellulosehydrate.

There are also described other processes in which a filament fromviscose spun in an acid bath is strongly drawn in hot water. In order toincrease the effect of the spinning baths and to augment the strength ofthe filaments, according to another process there were added bivalentsalts, for example zinc sulfate, to the baths and the filaments spun inthese baths were drawn in hot diluted acids.

Finally one had proposed to manufacture high tenacity artificial fibersand filaments by spinning the viscose into filaments in a spinning bathcontaining sulfuric acid and salts. After precipitation the filamentsleave the precipitating bath and are swollen in an alkaline bathcontaining zinc or aluminium. The swollen filaments are then drawn inthe swelling bath or after the swelling bath in the open air or in hotwater or in hot steam.

Our invention is based on the observation that it is possible to obtainhigh tenacity filaments in a simple way by using ordinary Miller-baths"of more than 7% sulfuric acid which, however, contain neither zinc norany other polyvalent metal, also without applying such swelling bathswhich contain polyvalent metal compounds. These filaments show hightenacities in the wet state their elongation being above 10%.

The new process consists in spinning viscose in a spinning bathcontaining sodium sulfate and sulfuric acid with a sulfuric acid contentof, for example, l0-14%. 'I'he freshly spun filaments are then swollenin a hot alkaline swelling bath not containing any polyvalent metalcompounds and the swollen filaments are strongly drawn either in theswelling bath or in separate hot salt solutions or in hot steam. The newinvention compared with former processes has the advantage that nopolyvalent metal compounds are necessary neither in the spinning bathnor in the swelling bath. Furthermore it has the advantage that spinningbaths containing sodium sulfate and 10-14% sulfuric acid are not soeasily disturbed during operation as baths with only 7% sulfuric acid.Compared with the known processes which contain no polyvalent metalsalts in the spinning baths or which employ these swelling baths atordinary temperature only, the new process yields filaments of betterphysical constants. The present invention is especially suitable formass production in the textile industry, since there it is necessary toattain the best effects in a most simple and inexpensive way.

In the manufacturing process an intermediate bath may be placed betweenthe acid spinning bath and the alkaline swelling bath which liberatesthe filament from the adhering acid and which prevents the alkali frombeing used up too quickly in the swelling bath. As'intermediate baththere may be advantageously employed at temperatures of 40-60 C. a waterbath containing salts and preferably wetting agents being stable in analkaline medium. The wetting agents being stable against alkalies areknown from literature, for example from the Textilhilfsmitteltabellen byDr. I. Hetzer, 2nd edition, Berlin 1938. The swelling bath itself on theother hand is used at temperatures above (3., preferably at temperaturesabove C. It consists of a 10-30% solution of sodium sulfate whichcontains 0.2-5% caustic soda. In such a swelling bath the freshly spunfilament still containing cellulose xanthate groups may be drawn fill-%of its original length.

During the manufacturing process according to the present inventionpreferablyhigh grade Example I A viscose of 8% ciliilos'e and 6.5%alkali is spun at a 'y-value' 45 "into a spinning bath containingsulfuric acid from a nozzle of 600 openings each of 0.07 mm. diameter.The spinning bath contains 10% sulfuric acid and 30% sodium sulfate andis kept at a temperature of 45-50 C. The filament is wound up from thenozzle with a speed of 25 meters and is conducted through the spinningbath a distance of cm. After leaving the precipitating bath the filamentis conducted a space of 60-80 cm. through a sodium sulfate solutionheated up at 50 C. and then a space of 80-100 cm. through a swellingbath which contains l-2% caustic soda and 20% sodium sulfate and is keptat a temperature of 95-100 C. During the passage through the swellingbath the filament is drawn 100% of its original length and finallyneutralized under tension in using sulfuric acid of a 5% concentration.The space in the neutralizing bath'is again 80-100 cm. The filamentsspun in this way have a dry tenacity of 3.3 grams per denier and a wettenacity of 2.2 grams per denier at an elongation of 12-15%.

Example II heated at 95 C. either directly after leaving theprecipitating bath or after passing an intermediate bath. The hot'swelling bath contains 2% caustic soda and sodium sulfate. Theintermediate bath which is put in after the precipitating bath andbefore the swelling bath consists of a 2% solution of sodium sulfate andis kept at 50 C. Sulfuric acid carried over by the filament into theintermediate bath is neutralized by caustic soda, so that the bathremains neutral all the time. The space of the filament in thewashingand swelling bath is around 80-100 cm. After leaving the swellingbath the filament is neutralized with diluted sulfuric acid. Thefilaments thus obtained possess a dry tenacity of 3.7 grams per denierand a wet tenacity of 2.6 grams per denier at an elongation of 12-15%.

Example III Manufacturing process as in Example I with the differencethat between the swelling bath tenacity of 2.4 grams per denier at anelongation of 12-14%.

Example IV ripening for 24 hours at 10 C. with 94 parts of an ordinarylowviscous viscose from sulfite cellulose with 8% cellulose, 6.5% alkali-value 45;,

time of fall of a steel ball 25 sec). The viscosity of the viscose aftermixing amounts to 44 sec. of the falling ball. The viscose is spun intoa filament at 45 C. from a bath consisting of 10% sulfuric acid and 30%sodium sulfate which after passing at 40 C. a feebly alkaline sodiumsulfate washing bath is drawn 100% at 95-100 C. in a bath containing10-20% sodiumsulfate and 1-2% caustic soda and is then neutralized. Thefilaments show a titre of the single filament of 1.8-2 and a drytenacity of 3.7-4 grams per denier, a wet tenacity of 2.4-2.6 grams perdenier and an elongation of 16-20%.

What we claim is:

1. The process for the manufacture of high tenacity artificial filamentsand fibers having an elongation above 10%, from viscose which comprisesspinning viscose, at least a portion of which was produced fromcellulose having a high a-cellulose content, in a spinning bathcontaining sodium sulfate and 10 to 14% sulfuric acid, swelling thefreshly spun filaments in a hot alkaline swelling bath at a temperatureabove 90 C. containing 10-30% sodium sulfate and..0.2-5% sodiumhydroxide, said spinning bath and-'said swelling bath being free ofpolyvalent metal compounds, and strongly drawing the freshly spunfilaments while heated from 50 to of their original length.

2. The process for the manufacture. of high tenacity artificialfilaments and fibers having an elongation above 10% from viscose whichcomprises spinning viscose, at least a portion of which was producedfrom cellulose having a high a-cellulose content, in. a spinning bathcontaining sodium sulfate and 10% to 14% sulfuric acid but free ofpolyvalent metal compounds, washing the freshly spun filaments in awashing bath at a temperature of 40-60 C. containing sodium sulfate anda wetting agent stable in an alkaline medium, swelling the washedfilaments in a hot alkaline swelling bath at a temperature above 90 C.containing Iii-30% sodium sulfate and 0.2-5% sodium hydroxide but freeof polyvalent metal compounds, and strongly drawing while heated thefreshly spun filaments from 50 to 100% of their original length.

3. The process as described in claim 1 in which the drawing of saidfilaments is effected in the swelling bath.

4. The process as described in claim 1 in which the drawing of saidfilaments is effected in a separate hot salt solution.

5. The process as described in claim 1 in which the drawing of saidfilaments is effected in hot steam. I

HEINRICH FINK. GASTON PLEPP.

